As understood in the prior art, a digital electronic still camera is a device which uses an electronic sensor to capture an image; signal processing to modify the captured image signal, e.g., as a function of ambient light, and to represent it numerically; and some storage device to preserve the numerical image data. Ordinarily, the image storage device is merely a receptacle for the image data.
It is further known for a digital electronic still camera to use a removable storage device, such as an integrated circuit memory card, to store images. For instance, U.S. Pat. No. 5,016,107 describes an electronic still camera utilizing image compression and providing digital storage in a removable memory card having a static random access memory. Software that controls the camera operation is located in non-removable programmable read only memory (PROM) integrated circuits in the camera. In this camera, the integrated circuits in the removable memory card store image data and a directory locating the data.
Other electronic camera systems described in the prior art record an image header along with the digital image data. The header typically describes some characteristics about the image or the camera. For instance, in U.S. Pat. No. 5,018,017, such header information indicates the classification of the information; the imaging system in use; the date and time; the compression mode; as well as image-specific information, such as flash use, white balance data, exposure value, and shutter speed. Furthermore, U.S. Pat. No. 5,153,729 shows memory capacity, a free area pointer, a battery expiration date, and a write inhibit flag in the header area of a memory card. Typically, each system conveys such characteristic data from the electronic camera by way of the memory card (where the data is temporarily stored) to a peripheral device, such as a player. The object is to increase the downstream functionality of the system by allowing utilization of image-related data in subsequent processing of the image data in a downstream peripheral device. The camera or imaging device generally utilizes little of the stored image characteristic data, one exception being data regarding the utilization of the storage device itself, i.e., how much memory space is remaining for further pictures. In the latter case, the camera accesses such data to display utilization to the camera user.
Coordination between a camera and a computer is generally shown in patent application Ser. No. 988,517, "Electronic Camera with Memory Card Interface to a Computer", which was filed on Dec. 10, 1992 and assigned to common assignee with the present application. This application describes a camera that is specially shaped so as to plug directly into the memory card slot of a portable computer; the camera is then usable as a unit with the portable computer. The camera contains EPROM memory with code for in-camera white balance and gamma correction, and also stores the compiled code which is used (by the computer) to operate the camera and to process the images from the sensor color filter array to obtain a full resolution, color corrected image. The image data is captured by the camera and directly downloaded to the computer, where it is processed with code obtained from the camera. As with prior memory card systems, the code is used downstream (in the computer) to process image data.
In a camera intended for acquisition of image data for use in a computer, such as described in Ser. No. 988,517, it is well understood that data corresponding to captured images may also be stored in a storage device that is capable of being removed from the camera. Such a storage device is often considered analogous to film in a conventional film camera. Just as it is known to encode film with marks that are useful in downstream processing of the film, it is also known for an electronic image storage device to contain non-image data which is useful in modifying the image data. Following the film analogy, such additional data is useful in downstream processing, such as in a computer, to modify the image data. Unlike film, however, the additional non-image data may be read by a variety of peripheral devices, including the camera itself. This provides an opportunity to deal with a number of imaging problems.
For instance, in most known electronic imaging systems, the software which controls the camera ordinarily cannot be updated without purchasing an entirely new camera, containing a lens, CCD image sensor, etc. (Albeit, a few high end film cameras utilize a removable program module from which the camera can download exposure algorithms.) It is well known that computer programs are updated more regularly than computer hardware, since the software can be refined to provide higher performance (i.e. better image quality) or more features while using the same hardware. An electronic camera can use a programmable digital processor controlled by software. Such a camera offers an opportunity for software updates, if the system is designed to facilitate such updates. What is needed is a method for software updates of the camera algorithms for higher performance, and for adding new features to a camera. Such a method should be quick and convenient for the user, preferably without requiring the use of additional storage modules. Existing memory devices are capable of limited two-way communication with an electronic camera, such as to report to the camera on memory space availability. An opportunity exists for enhancing such "upstream" communication to provide altogether new applications for an electronic camera.